The ICM survey found just 37 percent of respondents happy with Blair, giving the prime minister an overall approval rating of minus 17 points -- the difference between those who are happy and those who are not.

In the immediate aftermath of the Iraq war in April, Blair rode high on the so-called "Baghdad Bounce" with an approval rating of plus seven.

The British leader is facing calls to resign following the apparent suicide last week of weapons expert David Kelly, at the centre of a row over a government dossier used to justify war in Iraq.

The BBC claims Kelly was the source of its report in May that said Blair's office had "sexed-up" a dossier on Iraq's alleged weapons of mass destruction.

ICM began carrying out its survey on Friday, the day police said they had found a body matching Kelly's description. Pollsters finished their work Sunday after police had formally identified the body.

The poll, published in The Guardian newspaper, showed only 39 percent of voters found Blair trustworthy and support for his Labour party at 36 percent -- down two points from last month and five since May.

The main opposition Conservatives remained unchanged on 34 percent and Britain's third party the Liberal Democrats were up one point to 22 percent. Britain's next general election is due by mid-2006 at the latest.

In a separate poll published in The Sun, a quarter of voters who backed Labour at the last election in 2001 said they had since switched to a rival party.

The Mori poll, published in Tuesday's edition of the tabloid, showed that most who deserted Blair had done so because of a lack of trust in the government's ability to improve public services.

WAR.WIRE